Synergistic stabilizing compositions



United States PatentO 2,729,690 I SYNERGISTI C STABILIZING COMPOSITIONS No Drawing. Application October 26, 1951, Serial No. 253,457

7 Claims. (Cl. 260-799) This invention relates to the stabilization of organic materials normally susceptible to deterioration. More particularly my invention relates to the inhibition of attack by oxygen and the prolongation of the useful life of oxygen-sensitive materials.

Hydrocarbon fuels for internal combustion engines may be broadly classified into three categories, according to the use for which they are intended; fuels for automotive spark ignition engines, fuels for aircraft spark ignition engines, and fuels for compression ignition engines. Although each such fuel is composed essentially of hydrocarbons, the stability characteristics during the manufacturing process and subsequent storage and use, particularly in the presence of oxygen, differs considerably, for each type. For example, typical automotive fuels contain straight and branched chain aliphatics, olefins, naphthenes and some aromatics, while typical aircraft fuels contain smaller proportion of olefins.' In recent years fuels for compression ignition engines have contained an increased proportion of cracked stocks, resulting in a higher olefin content and consequent increase in the susceptibility to gum formation. The effect of the deterioration of thefuel upon each type of engine may diifer, but equivalent processes of deterioration occur in each fuel. For example, the formation of gum in fuels designed for use in spark ignition engines interferes with normal operation of the ignition system and valvesywhile the formation of such gummy materials in compression ignition engine fuels interferes with the normal operation of the fuel filters and injectors in such engines.

In general, the hydrocarbons present-in automotive gasolines are more susceptible to degradation than those comprising aircraft fuels. However, both automotive and aircraft fuels are commonly blended with tetraethyllead before use. Such blending impose sa further point of instability in the finished fuel, since the tetraethyllead is susceptible to some deterioration by contact with'oxygen during the blending, storage and handling operations, with consequent formation of haze, loss of some antiknock value, and lessened performance in the engine. This point of attack is often overlooked and is ordinarily unimportant in automotive fuels, as the protective measures necessary for the base stock are usually more than suflicient to protect the tetraethyllead. If, however, a. stabilizing ingredient were added which is capable of protecting only the fuel, the attack upon the tetraethyllead would then become apparent. In aircraft fuels the protection must center upon the antiknock additive, as the fuel itself is relatively stable. Furthermore, this phase of the problem becomes relatively more important in aircraft fuels, since the tetraethyllead content of such fuels is generally several times that present'in automotive fuels.

Heretofore, the protection of fuels for internal combustion engines effectively against the two above-described separate but related deleterious effects of contact with oxygen during the refining, manufacturing, blending, storage and handling operations has been accomplished only with difliculty. Furthermore, because of the specificaessential that any material used to protect such fuelsagainst deterioration be effective in extremely small quantities, on the order of one pound of additive per five thousand gallons of fuel, so that secondary problems do no arise through their use.

Similarly, synthetic and natural elastomers are susceptible to absorption of oxygen with consequent destruc-- tion of certain useful physical properties and with the introduction of certain properties which render articles manufactured from such elastomers of limited utility. By absorption of oxygen such elastomers deteriorateprematurely, lose tensile strength and flexibility, andb'ecome'- discolored and embrittled. While certain materials have been proposed for the protection of such elastomers from the deleterious action of oxygen, most of such protective substances, as for example ,B-naphthol, possess the serious disadvantage, particularly with respect to light colored stocks, that their own degradation products are themselves colored and hence interfere with the color fastness of the stocks being protected.

Further examples of materials which must be protected from the deleterious effects of oxygen includes mineral oils, such as lubricating oils, soaps, certain perishable foodstuifs, such as animal and vegetable oils and fats, and synthetic unsaturated organic materials. In general, such organic substances may require protection at any time during the processes of manufacturing, handling, storage and use when they become exposed to and absorb oxygen with deleterious efiects.

It .is, therefore, an object of my invention to provide means for protecting such organic substances which deteriorate in or are affected adversely by oxygen. It is a further object of my invention to provide a class of mixtures which provides the required protection against the formation of gummy oxidation and polymerization products of unstable hydrocarbons onicontact with oxygen at reduced levels of additive. Another object of this invention is to provide means for increased stabilization of hydrocarbon fuels for internal combustion spark, and compression ignition engines during the manufacturing, handling and storage of such fuels prior to their use without increasing the total amount of stabilizing additive. Likewise, it is an object of my invention to provide means for reducing the antioxidant requirement of unstable organic materials. A still further object of this invention is to provide hydrocarbon fuels containing tetraethyllead which do not deteriorate in contact with oxygen with the resultant formation of gum, haze and tetraethyllead oxidation products. It is also an object of the presentin vention to provide fuels containing tetraethylleadin whicl there is essentially no loss in performancecharacteristics due to such deterioration of the tetraethyllead during blending, storage and handling. Likewise it is an object of my invention to provide means for preventing embrit tlement, discoloration, loss of tensile strength'and other harmful effects in elastomers during the milling; compounding, fabrication, storage, handling'and use of such elastomer stocks. A further object of my invention is to provide means for protecting other perishable natural or synthetic organic materials from the adverse effects of contact with oxygen. Still further objects will appearfrom the description of this invention as hereinafter dis;- closed. y

The above objects can be accomplished by addingto oxygen-sensitive organic materials a small proportionof a composition comprising arylamine antioxidant mate rials and substances derived from the class of hydraaine.

I have made the discovery that hydrazines, themselvesincapable of affording effective protection to organic terials against deterioration in the presence of oxygen,

rammed Jan. 3, i956- have the property of greatly increasing the effectiveness of previously known, expensive antioxidants of the arylamine type. Such hydrazines I refer to hereinafter as synergists. The hydrazines of my invention include those which are monoor di-substituted on one or both of the nitrogen atoms with hydrocarbon radicals, heterocyclic radicals, and certain functionally substituted hydrocarbon radicals as well as the material hydrazine itself. Among the hydrocarbon radicals which I have found to be effective substituents of the hydrazine synergists of my invention are alkyl, aryl and aralkyl, for example, methyl, ethyl, propyl, isopropyl, amyl, iso-arnyl, ter.-amyl, hexyl, 2-methy1hexyl, dodecyl, stearyl, allyl, crotyl, phytyl, oleyl, phenyl, a-naphthyl, S-naphthyl, tolyl, xylyl, benzyl, B-phenethyl, and the like. As examples of heterocyclic radicals effective in my synergists I include the furfuryl group, the quinoline group, the acridine group and the like. The functionally substituted hydrocarbon radicals of such synergistic hydrazines include alkoxyphenyl, alkoxyalkyl and the like. In general, 1' prefer to employ those hydrazines which are mono-substituted on one nitrogen atom, primarily because of their greater availability, ease of manufacture and economy. However, it is within the scope of my invention to employ as synergists with arylamine antioxidants those hydrazines substituted as above on the N-, N,N-, N,N'-, N,N,N- or N,N, N,N- atoms.

I have found that the replacement of a portion of the arylamine antioxidant of a stabilized composition with an equal weight of my synergistic hydrazines results in a stabilized composition which is more resistant to attack by oxygen. Likewise addition of one of my hydrazines to an arylamine-treated oxygen-sensitive substance greatly improves the stability thereof. Furthermore, to attain a specified degree of oxygen or ozone stability the re quired amount of my arylamine-hydrazine mixture is less than the required amount of the arylamine antioxidant alone. Typical of the arylamine antioxidants which are activated by my hydrazine synergists include N,N-disec.-butyl-p-phenylenediamine, N-n-butyl-p-aminophenol, N-isobutyl-p-aminophenol, N,N' di-ix-naphthyl-p-phenylenediamine, N,N' di isopropyl-p-phenylenediamine, N- phenyl-fl-nahthylamine and the like.

'In general, in addition to hydrazine itself, my synergistic hydrazines comprise organs-substituted hydrazines wherein the organic radical is not of itself a strongly antioxidant forming material. In general terms I do not contemplate aryl hydrazines wherein the aryl group is substituted with a nitrogen group or an hydroxyl group, as such derivatives would be expected to exhibit considerable antioxidant activity in themselves and the synergistic effect would not be present.

The absorption of oxygen by hydrocarbon fuels can be measured directly by the standard method of the American Society of Testing Materials for determination of the Oxidation Stability of Gasoline (induction Period Method), ASTM designation: D52546, as fully described in Part III-A, ASTM Standards for 1946. According to this method the induction period is the period during which there is no absorption of oxygen by the test material as indicated by a drop in pressure, when placed in a testing bomb maintained at a temperature of 100 C. with an initial pressure of 169 pounds per square inch gauge of oxygen. The Induction Period Increase (IPI) is the increase in the duration of this period caused by the addition of a protective substance, and is a direct measure of the protection afforded by such additive. Thus, the longer the IPI the more effective is the stabilizer. To obtain the results shown herein, 6 milligrams of the additive was dissolved in 100 milliliters of the gasoline. Where the solubility characteristics of the material were such that this concentration could not be obtained, a small amount of a solubilizing agent, such as ethyl or isopropyl alcohol, was added in amount up to 2 per cent of the gasoline.

4 TABLE I Efiect on induction period increase of gasoline Synergist: IPI

Hydrazine 0 Methyl hydrazine 0 2-quinolyl hydrazine 5 3-quinolyl hydrazine 0 p-Methoxyphenyl hydrazine 0 N-phenyl-N-benzyl hydrazine 50 In a similar manner it is established that other typical examples of my synergizing hydrazines are ineffective or moderate antioxidants when employed in the absence 1 of an arylamine antioxidant: ethyl hydrazine, N,N-dimethyl hydrazine, N,N-di-isopropyl hydrazine, N-phenyl- N-amyl hydrazine, N,N'-a-naphthyl-N-methyl hydrazine, N,N-dipr0pyl-N',N'-diphenyl hydrazine, N-phenyl- N-benzyl-N'-methyl-N'-ally1 hydrazine, allyl hydrazine, t-butyl hydrazine, dodecyl hydrazine, N-st'earyl-N- phenyl hydrazine,'N-oleyhN-methyl hydrazine, N,N-diphenyl hydrazine and the like.

From Table I it is clear that the synergizing components of the antioxidant mixtures of this invention are essentially inert, or weak antioxidants.

The effectiveness of the hydrazines of my invention as synergists is typified in Table II, wherein the hydrazines were added to the test gasoline in admixture with N,N'- di-sec.-butyl-p-phenylenediamine. I have listed in Table II the increase in the induction period of the so-treated gasoline at a total concentration of 6 milligrams of the mixture containing 33 weight per cent of the hydrazine per milliliters of gasoline, and the increase in the induction period of the test gasoline treated with the arylamine antioxidant alone at the same concentration of 6 milligrams total per 100 milliliters of gasoline.

TABLE II Efiect on induction period increase of gasoline IPI IPI with 6 Expect- N o. Synerglst fif gg ml. of

I I synerantioxi- EtIeet gistic dant mixture Hydraztne 595 395 695 2 Qulnolyl hydrazine 596 397 670 3-Qulnolyl hydrazine 595 395 575 Methyl hydrazine 595 395 880 N-Phenyl-N-benzyl zine 595 410 650 By reference to Table II the synergism is apparent. Thus, for example, replacing 33 per cent of the antioxidant with an equal weight, of hydrazine increases the induction period increase of the fuel in spite of the fact that only 67 per cent of the antioxidant is employed. Thus, to obtain an IPI of 880, as in No. 4, using N,N-disec..-butyl-p-phenylenediamine alone would require 8.9 milligrams of the antioxidant. However, this was actually achieved with 4.0 milligrams of the antioxidant plus 2.0 milligrams of the hydrazine;

The above induction period determination is only one method of proving. the efliciency of an antioxidant material. Another widely used method of establishing the stability of a hydrocarbon fuel comprises storing a sample of the fuel for a period of several months at a temperature of F. and determining from time to time the amount of gum formed in the stored fuel by the so-called Air Jet Evaporation method, ASTM Designation D38146, fully described in ASTM Standards for 1946, part III-A. The synergistic antioxidant compositions of my invention when employed in amount between about 0.1 and about l5 milligrams per 100 milliliters of fuel produced extremely effective protection to commercial motor gasolines, both with and without tetraethyl-lead antiknock fluids.

Thus the incorporation in such fuels of other additives such as antiknock compounds does not interfere with the operation of my synergistic antioxidant compositions.

Mixtures of the hydrazine synergists of my invention when employed along with known arylamine rubber antioxidants likewise provide protection to such rubber stocks. This can be determined by measuring the degree to which a test piece so compounded retains its elasticity after being subjected to accelerated aging according to the procedure of ASTM Designation D-572-42, for a period of 96 hours at a temperature of 70 C. in the presence of oxygen pressure initially at 300 pounds per square inch gauge. By determining both the .tensile strength and ultimate elongation of such test pieces it is found that my hydrazine synergists greatly improve the functioning of arylamine antioxidants and overcome some of their inherent disad vantages, such as migration and bleeding.

The quantities of the mixtures of my invention incorporated in the materials to be stabilized are not critical and depend largely upon the type of material being stabilized and the conditions under which the exposure to oxygen occurs. For example, with gasolines, tetraethyllead, mineral oils and similar materials the mixtures of my invention are preferably employed in concentrations between the limits of approximately 0.1 and 15 milligrams per 100 milliliters of material to be stabilized. For other materials, such as for example elastomers, both natural and synthetic, somewhat larger amounts of the stabilizers of my invention are preferred and can be tolerated. Thus, in such materials I employ between approximately 0.1 and 2 parts of synergistic mixture per 100 parts of oxidizable material. Thus, my mixtures can be satisfactorily employed in a wide range of concentrations, and I do not intend that my invention be restricted to the specific quantities mentioned herein.

Furthermore, I do not mean to be restricted by the ratios of synergistic hydrazine to arylamine antioxidant employed in the specific embodiments of my invention disclosed herein by way of examples. Such ratios will be determined in part by the nature of the material to be stabilized, in part by the specific arylamine employed and in part by the specific synergistic hydrazine. In general,

however, I prefer to employ between about 30 and 100.

parts by weight of hydrazine to parts by weight of arylamine.

I have disclosed a number of preferred embodiments of my invention and illustrated several means whereby protection can be afforded to organic materials sensitive to attack by oxygen. My invention is not intended to be limited to the specific embodiments of my invention herein or to the means described herein for obtaining the advantages possible in employing my synergistic mixtures, as other methods of practicing my invention will be apparent to those skilled in the art.

I claim:

1. The composition of claim 7 wherein said arylamine antioxidant is a naphthylamine.

2. The composition of claim 7 wherein said hydrazine is hydrazine.

3. The composition of claim 7 wherein said hydrazine is methyl hydrazine.

4. The composition of claim 7 wherein said hydrazine is Z-quinolyl hydrazine.

5. The composition of claim 7 wherein said hydrazine is 3-quinolyl hydrazine.

6. The composition of claim 7 wherein said hydrazine is p-methoxyphenyl hydrazine.

7. A composition comprising rubber stabilized by the presence of between about 0.1 and 2.0 parts per 100 parts of rubber of a synergistic antioxidant composition consisting essentially of an arylamine antioxidant, and a by drazine, said hydrazine being present in amount between about 30 and 100 parts per 100 parts of said arylamine.

References Cited in the file of this patent UNITED STATES PATENTS 1,793,635 Reed Feb. 24, 1931 2,062,675 Rather et al Dec. 1, 1936 2,136,373 Busse Nov. 15, 1938 2,166,223 Semon July 18, 1939 FOREIGN PATENTS 423,938 Great Britain of 1933 505,113 Great Britain May 4, 1939 

7. A COMPOSITION COMPRISING RUBBER STABILIZED BY THE PRESENCE OF BETWEEN ABOUT 0.1 AND 2.0 PARTS PER 100 PARTS OF RUBBER OF A SYNERGISTIC ANTIOXIDANT COMPOSITION CONSISTING ESSENTIALLY OF AN ARYLAMINE ANTIOXIDANT, AND A HYDRAZINE, SAID HYDRAZINE BEING PRESENT IN AMOUNT BETWEEN ABOUT 30 AND 100 PARTS PER 100 PARTS OF SAID ARYLAMINE. 